[jpr703]

I've noticed that most MPX3 users here seem to be Sennheiser fans, so finding advice on tubes to match my RS-1s has been difficult. Now that I've had my amp for a couple months, I've done quite a bit of tube rolling and thought I'd post a few of my favorite combinations. If you're using Grado's with your tube amp, please feel free to post your favorites as well.

1. (1) RCA clear glass 6SN7 and (2) Sylvania 5687s. This is by far my favorite. The sound is quick and detailed, but very natural and not fatiguing. I've also tried a Tung-Sol 6SN7 in the driver position, but it was just too bright. Using a Sylvania 6SN7 gave a sound that was a little too "ethereal" for my liking. I have a set of RCA 5687's on order that I intend to try in this arrangement and I'll post a follow-up when I've had a chance to compare them to the Sylvanias.

2. (1) Unmarked black glass 6BL7 and (2) Sylvania 5687s. This is a little more "tuby" sounding than the first combo and looses just a little bit of the bass and midrange. However, vocals are absolutely fantastic with these tubes. I've also tried Tung-Sol 5687s but they were a little harsh at the high end with the Grados. I'll also try the RCA 5687s in this arrangement when they come in.

I wish I knew who manufactured the black glass 6BL7 because it sounds significantly better than 3 other 6BL7 tubes I've tried in the same configuration. Unfortunately there are no markings on the tube at all, save a very faint white "stop sign" with "6BL7" written in it. There is also a small silver band that runs around the base of the glass. If you know what it is, please let me know!

3. (1) Tung-Sol 6SN7 and (2) Sylvania 6SN7s. A very "natural" sounding set of tubes that sounds very good on vocals and slower-paced music. If I listenend mostly to pop or classical, this might be my first choice. Unfortunately, it lacks some speed and attack with rock music. Using a Sylvania or RCA in the driver position seems to slow it down even more. Also, every tube in this arranagement is expensive!

 

[sacd lover]

Quote:

Originally Posted by jpr703 I wish I knew who manufactured the black glass 6BL7 because it sounds significantly better than 3 other 6BL7 tubes I've tried in the same configuration. Unfortunately there are no markings on the tube at all, save a very faint white "stop sign" with "6BL7" written in it. There is also a small silver band that runs around the base of the glass. If you know what it is, please let me know!

The white stop sign is usually indicative of an RCA tube. So is the silver band that runs around the base of the tube. I see that silver band on a lot of older RCA 6sn7's with lightly smoked gray glass. Could the black glass be considered a dark charcoal? Dark gray/ charcoal glass tubes are usually RCA's too.

Sometimes I see the white stop sign type marking on my TS D getter 5687 tubes. All the black glass tubes I have used were from Tung Sol, Ken Rad and National Union .... with the charcoal glass tubes being from RCA. Guessing from this information, I would suspect the 6bl7gt tube is either a RCA or a Tung Sol.

 

[jpr703]

I'd definitely call the glass black. You can barely see through it, even holding it up to the light. Curiously enough though, the dome of the tube is clear and you can see a rectangular plate with several holes punched in it. There are four tiny brass pins that come up through the plate as well.

Flipping the tube upside down, I did notice some words embedded in the black plastic, next to the base pins. It says, "Liscensed Only to Extent Indicated on Carton."

 

[Gabe Logan]

From your description it sure sound like a ken rad but it would have said that on the base and it is a 6SN7 anyways.

Time to look at photos.

 

[PFKMan23]

Ken Rad Black GLass and the 6BX7GT is what I like with my Grados, and k701s as well. I also actually like the 3 x RCA 12sn7GT but that's baically too dark for almost everyone, and heh the more powerful output tubes do help alot.

 

[Rob N]

In my SDS-XLR I've been using a pair of Brimar brownbase 6SN7's followed by a quad of National Union grey glass 6SN7's.

This is the warmest and smoothest the SDS-XLR has sounded so far.

 

[jpr703]

After doing some research, I found out that the unmarked black-glass tube that I thought was a 6BL7 is actually a Ken-Rad 6SN7. After trying a few different tubes that I'm sure are 6BL7s, it became pretty clear to me that the 6SN7 driver with 5687s in the outputs was my favorite combo.

Since my original post, I tried several other different tube brands and combinations in this same basic configuration and I've finally settled on a favorite.

I've been using a RCA grey-glass VT-231 (military version of the 6SN7) and a pair of Raytheon 5687s for some time now. This combination doesn't have as crystal clear of a presentation as other combinations I've tried, but it does have some serious "boogie" to the sound and allows you to keep the detail while losing the fatigue. It really draws me into the music and makes me fall in love with my RS-1s all over again.

If you want to spice up the sound a little more, you could always use the same driver tube and switch out the 5687s for Tung-Sols or Sylvanias.